Abstract
The effect of combining procedures of high hydrostatic pressure (HHP) with alkaline electrolyzed water (AlEW) on the injury characteristics of bacterial spores was investigated. Effective reductions of survival Bacillus subtilis spores by a combination treatment of AlEW with HHP were obtained after the treated spores were heat shocked at 80°C for 15 min. No survival was observed by applying 100 MPa of HHP treatment. Approximately 90 to 99% of Bacillus spores treated by HHP with AlEW were injured or lost heat resistance and there were 1 to 2 logs differences in the survival comparing with the unheated spores. Double culture method (DCM) for assessing the injury characteristics of bacterial spores was performed by using trypticase soy broth supplemented with chloramphenicol (CP) or rifampicin (RFP), which were related to the synthesis inhibition of protein and RNA, respectively. Severe injury of the treated bacterial spores assessed by RFP supplemented broth was obtained at 50 MPa with and without AlEW. Especially at 50 MPa, considerable synergistic effect of HHP and AlEW on spore injury was observed. These results suggested that injury associated with the biosynthesis of some enzymes was observed at relatively low pressure level.
